Piezoelectric film transducer

ABSTRACT

A method and apparatus transduces between mechanical and electrical signals within a middle ear to improve hearing. An electromechanical transducer film, preferably polyvinylidene fluoride (PVDF), is carried by a mount secured to the middle ear. The film is constrained by the mount, or by the mount and an auditory element. The invention includes substantially straight, bow-shaped, hoop-shaped, and bi-element transducer film embodiments. The film transduces between mechanical vibrations of an auditory element, such as the malleus or stapes, and electrical signals for use with an electronics unit of a partial middle ear implantable (P-MEI) or total middle ear implantable (T-MEI) hearing aid.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 08/689,312 entitled PIEZOELECTRIC FILM TRANSDUCER,filed on Aug. 7, 1996.

THE FIELD OF THE INVENTION

[0002] This invention relates to an electromechanical transducer for usein a hearing system implantable in a middle ear.

BACKGROUND

[0003] In some types of partial middle ear implantable (P-MEI) or totalmiddle ear implantable (T-MEI) hearing aid systems, sounds producemechanical vibrations which are transduced by an electromechanical inputtransducer into electrical signals. These electrical signals are in turnamplified and applied to an electromechanical output transducer. Theelectromechanical output transducer vibrates an ossicular bone inresponse to the applied amplified electrical signals, thereby improvinghearing.

[0004] Such electromechanical input and output transducers should beproportioned to provide convenient implantation in the middle ear. Lowpower consumption transducers are also desired for use with a limitedlongevity implanted battery as a power source. The electromechanicalinput transducer should have high sensitivity, gain, linearity, and awide dynamic range in producing electrical signals from a sensedmechanical vibration. The electromechanical output transducer shouldhave low power consumption in producing mechanical vibrations from anapplied electrical input signal.

SUMMARY OF THE INVENTION

[0005] The invention provides a piezoelectric transducer film disposedwithin the middle ear and a method of use, such as with a middle earimplantable (MEI) hearing system including a partial middle earimplantable (P-MEI) hearing aid system or a total middle ear implantable(T-MEI) hearing aid system.

[0006] In one embodiment, the invention is used as an electromechanicaloutput transducer. A mount carrying a piezoelectric transducer film issecured to the middle ear. An electrical input signal is applied to thefilm to dynamically vary the film length. The film is constrained suchthat variations in the film length produce positional film variationswhich are mechanically coupled to vibrate an auditory element.

[0007] In one embodiment, as an electromechanical output transducer, thefilm is mechanically coupled to first and second constraint points, suchas on the mount, or on the mount and on the auditory element. The filmis optionally bowed away from the mount. A variation in film lengthbetween the first and second constraint points is transformed into apositional variation of a driving point of the film. The driving pointof the film couples mechanical vibrations to an auditory element such asthe stapes.

[0008] In another embodiment, a hoop-shaped piezoelectricelectromechanical output transducer film (hoop) is mechanically coupledto the mount at a coupling point. The hoop is coupled to first andsecond constraint points on first and second arms extending radiallyoutward from the mount. An applied electrical input signal causesvariations in a circumferential length of the hoop. The variations inthe circumferential length of the hoop are transformed into positionalvariations that are typically approximately orthogonal to a longitudinaldirection of the mount as a result of constraining by the first andsecond arms. The positional variations couple mechanical vibrations toan auditory element such as the stapes.

[0009] In another embodiment, the invention is used as anelectromechanical input transducer. A mount carrying a piezoelectrictransducer film is secured to the middle ear. The film is coupled to anauditory element, such as the malleus, for receiving mechanicalvibrations resulting from sound waves. The film transducer produces anoutput voltage in response to the mechanical vibrations. The film ismechanically coupled to first and second constraint points, such as onthe mount, or on the mount and on the auditory element.

[0010] In one embodiment, as an electromechanical input transducer, thefilm is mechanically coupled to the mount at first and second constraintpoints. The film is optionally bowed away from the mount. The film iscoupled to an auditory element, such as the malleus, at a vibrated pointbetween the first and second constraint points. Received vibrationsconstrain the length of the film, producing an electrical output signalin response.

[0011] In another embodiment, as an electromechanical input transducer,a hoop-shaped film is mechanically coupled to the mount at a couplingpoint. The film is coupled to first and second constraint points onfirst and second arms extending radially outward from the mount. Avibrated point on the film is coupled to an auditory element, such asthe malleus. Received vibrations constrain the circumferential length ofthe film, producing a resulting electrical output signal in response.

[0012] Thus, the invention includes an electromechanical inputtransducer film receiving mechanical vibrations from an auditory elementand providing a resulting electrical signal to an electronics unit of animplantable hearing system. The invention also includes anelectromechanical output transducer film receiving electrical signalsfrom the electronics unit of an implantable hearing system and vibratingan auditory element in response. The invention also provides anelectronics unit and a programmer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In the drawings, like numerals describe like componentsthroughout the several views.

[0014]FIG. 1 illustrates a frontal section of an anatomically normalhuman right ear in which the invention operates.

[0015]FIG. 2 is a schematic illustration of the right side of a person'shead and neck regions.

[0016]FIG. 3 is a schematic illustration of one embodiment of theinvention having a bow-shaped piezoelectric output transducer film.

[0017]FIG. 4 is a schematic illustration of another embodiment of theinvention having a bow-shaped piezoelectric input transducer film.

[0018]FIG. 5 is a schematic illustration of another embodiment of theinvention having a hoop-shaped piezoelectric output transducer film.

[0019]FIG. 6 is a schematic illustration of another embodiment of theinvention having a hoop-shaped piezoelectric input transducer film.

[0020]FIG. 7 is a schematic illustration of another embodiment of theinvention having a substantially straight piezoelectric outputbi-element transducer film.

[0021]FIG. 8 is a schematic illustration of another embodiment of theinvention having a substantially straight piezoelectric input bi-elementtransducer film.

[0022]FIG. 9 is a schematic illustration of another embodiment of theinvention having a piezoelectric output transducer film, constrained ata mount and at a driving point.

[0023]FIG. 10 is a schematic illustration of another embodiment of theinvention having a piezoelectric input transducer film, constrained at amount and at a vibrated point.

[0024]FIG. 11 is a schematic illustration of one embodiment of theinvention including an implanted hearing assistance device and anexternal programmer.

DETAILED DESCRIPTION

[0025] The invention provides an electromechanical transducer which isparticularly advantageous when used in a middle ear implantable hearingsystem such as a partial middle ear implantable (P-MEI), total middleear implantable (T-MEI), or other hearing aid system. A P-MEI or T-MEIhearing aid system assists the human auditory system in convertingacoustic energy contained within sound waves into electrochemicalsignals delivered to the brain and interpreted as sound. FIG. 1illustrates generally the use of the invention in a human auditorysystem. Sound waves are directed into an external auditory canal 20 byan outer ear (pinna) 25. The frequency characteristics of the soundwaves are slightly modified by the resonant characteristics of theexternal auditory canal 20. These sound waves impinge upon the tympanicmembrane (eardrum) 30, interposed at the terminus of the externalauditory canal 20, between it and the tympanic cavity (middle ear) 35.Variations in the sound waves produce tympanic vibrations. Themechanical energy of the tympanic vibrations is communicated to theinner ear, comprising cochlea 60, vestibule 61, and semicircular canals62, by a sequence of articulating bones located in the middle ear 35.This sequence of articulating bones is referred to generally as theossicular chain 37. Thus, the tympanic membrane 30 and ossicular chain37 transform acoustic energy in the external auditory canal 20 tomechanical energy at the cochlea 60.

[0026] The ossicular chain 37 includes three primary components: amalleus 40, an incus 45, and a stapes 50. The malleus 40 includesmanubrium and head portions. The manubrium of the malleus 40 attaches tothe tympanic membrane 30. The head (if the malleus 40 articulates withone end of the incus 45. The incus 45 normally couples mechanical energyfrom the vibrating malleus 40 to the stapes 50. The stapes 50 includes acapitulum portion, comprising a head and a neck, connected to afootplate portion by means of a support crus comprising two crura. Thestapes 50 is disposed in and against a membrane-covered opening on thecochlea 60. This membrane-covered opening between the cochlea 60 andmiddle ear 35 is referred to as the oval window 55. Oval window 55 isconsidered part of cochlea 60 in this patent application. The incus 45articulates the capitulum of the stapes 50 to complete the mechanicaltransmission path.

[0027] Normally, prior to implantation of the invention, tympanicvibrations are mechanically conducted through the malleus 40, incus 45,and stapes 50, to the oval window 55. Vibrations at the oval window 55are conducted into the fluid-filled cochlea 60. These mechanicalvibrations generate fluidic motion, thereby transmitting hydraulicenergy within the cochlea 60. Pressures generated in the cochlea 60 byfluidic motion are accommodated by a second membrane-covered opening onthe cochlea 60. This second membrane-covered opening between the cochlea60 and middle ear 35 is referred to as the round window 65. Round window65 is considered part of cochlea 60 in this patent application. Receptorcells in the cochlea 60 translate the fluidic motion into neuralimpulses which are transmitted to the brain and perceived as sound.However, various disorders of the tympanic membrane 30, ossicular chain37, and/or cochlea 60 can disrupt or impair normal hearing.

[0028] Hearing loss due to damage in the cochlea is referred to assensorineural hearing loss. Hearing loss due to an inability to conductmechanical vibrations through the middle ear is referred to asconductive hearing loss. Some patients have an ossicular chain 37lacking sufficient resiliency to transmit mechanical vibrations betweenthe tympanic membrane 30 and the oval window 55. As a result, fluidicmotion in the cochlea 60 is attenuated. Thus, receptor cells in thecochlea 60 do-not receive adequate mechanical stimulation. Damagedelements of ossicular chain 37 may also interrupt transmission ofmechanical vibrations between the tympanic membrane 30 and the ovalwindow 55.

[0029] Various techniques have been developed to remedy hearing lossresulting from conductive or sensorineural hearing disorder. Forexample, tympanoplasty is used to surgically reconstruct the tympanicmembrane 30 and establish ossicular continuity from the tympanicmembrane 30 to the oval window 55. Various passive mechanical prosthesesand implantation techniques have been developed in connection withreconstructive surgery of the middle ear 35 for patients with damagedelements of ossicular chain 37. Two basic forms of prosthesis areavailable: total ossicular replacement prostheses (TORP), which isconnected between the tympanic membrane 30 and the oval window 55; andpartial ossicular replacement prostheses (PORP), which is positionedbetween the tympanic membrane 30 and the stapes 50.

[0030] Various types of hearing aids have been developed to compensatefor hearing disorders. A conventional “air conduction” hearing aid issometimes used to overcome hearing loss due to sensorineural cochleardamage or mild conductive impediments to the ossicular chain 37.Conventional hearing aids utilize a microphone, which transduces soundinto an electrical signal. Amplification circuitry amplifies theelectrical signal. A speaker transduces the amplified electrical signalinto acoustic energy transmitted to the tympanic membrane 30. However,some of the transmitted acoustic energy is typically detected by themicrophone, resulting in a feedback signal which degrades sound quality.Conventional hearing aids also often suffer from a significant amount ofsignal distortion.

[0031] Implantable hearing aid systems have also been developed,utilizing various approaches to compensate for hearing disorders. Forexample, cochlear implant techniques implement an inner ear hearing aidsystem. Cochlear implants electrically stimulate auditory nerve fiberswithin the cochlea 60. A typical cochlear implant system includes anexternal microphone, an external signal processor, and an externaltransmitter, as well as an implanted receiver and an implanted singlechannel or multichannel probe. A single channel probe has one electrode.A multichannel probe has an array of several electrodes. In the moreadvanced multichannel cochlear implant, a signal processor convertsspeech signals transduced by the microphone into a series of sequentialelectrical pulses corresponding to different frequency bands within aspeech frequency spectrum. Electrical pulses corresponding to lowfrequency sounds are delivered to electrodes that are more apical in thecochlea 60. Electrical pulses corresponding to high frequency sounds aredelivered to electrodes that are more basal in the cochlea 60. The nervefibers stimulated by the electrodes of the cochlear implant probetransmit neural impulses to the brain, where these neural impulses areinterpreted as sound.

[0032] Other inner ear hearing aid systems have been developed to aidpatients without an intact tympanic membrane 30, upon which “airconduction” hearing aids depend. For example, temporal bone conductionhearing aid systems produce mechanical vibrations that are coupled tothe cochlea 60 via a temporal bone in the skull. In such temporal boneconduction hearing aid systems, a vibrating element can be implementedpercutaneously or subcutaneously.

[0033] A particularly interesting class of hearing aid systems includesthose which are configured for disposition principally within the middleear 35 space. In middle ear implantable (MEI) hearing aids, anelectrical-to-mechanical output transducer couples mechanical vibrationsto the ossicular chain 37, which is optionally interrupted to allowcoupling of the mechanical vibrations to the ossicular chain 37. Bothelectromagnetic and piezoelectric output transducers have been used toeffect the mechanical vibrations upon the ossicular chain 37.

[0034] One example of a partial middle ear implantable (P-MEI) hearingaid system having an electromagnetic output transducer comprises: anexternal microphone transducing sound into electrical signals; externalamplification and modulation circuitry; and an external radio frequency(RF) transmitter for transdermal RF communication of an electricalsignal. An implanted receiver detects and rectifies the transmittedsignal, driving an implanted coil in constant current mode. A resultingmagnetic field from the implanted drive coil vibrates an implantedmagnet that is permanently affixed only to the incus 45. Suchelectromagnetic output transducers have relatively high powerconsumption, which limits their usefulness in total middle earimplantable (T-MEI) hearing aid systems.

[0035] A piezoelectric output transducer is also capable of effectingmechanical vibrations to the ossicular chain 37. An example of such adevice is disclosed in U.S. Pat. No. 4,729,366, issued to D. W. Schaeferon Mar. 8, 1988. In the '366 patent, a mechanical-to-electricalpiezoelectric input transducer is associated with the malleus 40,transducing mechanical energy into an electrical signal, which isamplified and further processed. A resulting electrical signal isprovided to an electrical-to-mechanical piezoelectric output transducerthat generates a mechanical vibration coupled to an element of theossicular chain 37 or to the oval window 55 or round window 65. In the'366 patent, the ossicular chain 37 is interrupted by removal of theincus 45. Removal of the incus 45 prevents the mechanical vibrationsdelivered by the piezoelectric output transducer from mechanicallyfeeding back to the piezoelectric input transducer.

[0036] Piezoelectric output transducers have several advantages overelectromagnetic output transducers. The smaller size or volume of thepiezoelectric output transducer advantageously eases implantation intothe middle ear 35. The lower power consumption of the piezoelectricoutput transducer is particularly attractive for T-MEI hearing aidsystems, which include a limited longevity implanted battery as a powersource. The invention provides an piezoelectric electromechanicalinput/output transducer for disposition within middle ear 35 and for usewith a P-MEI, T-MEI, or hearing system.

[0037]FIG. 2 is a schematic diagram illustrating a view of the rightside of a person's head 70 and neck 75. Outer ear 25 is slightly pulledanteriorly, to expose a region of the temporal bone known as the mastoid80. An incision is made in the skin covering the mastoid 80, and anunderlying access hole 85 is created through the mastoid 80, allowingexternal access to the middle ear 35. The access hole 85 is locatedapproximately posterior and superior to the external auditory canal 20.By placing the access hole 85 in this region, a transducer is disposedwithin the middle ear 35 cavity.

[0038]FIG. 3 illustrates middle ear 35 in more detail, in which oneembodiment of the invention is used as an electromechanical outputtransducer. FIG. 3 includes external auditory canal 20, tympanicmembrane 30, malleus 40, stapes 50, oval window 55, cochlea 60, and aportion of mastoid 80. Incus 45 has been removed, though this is notrequired for operation of the invention. A mount 100 is cantileveredfrom its proximal end, which is secured to mastoid 80. A distal end ofmount 100 extends longitudinally from the proximal end of mount 100 intomiddle ear 35. Mount 100 comprises any rigid biocompatible material.Examples of biocompatible materials include titanium, stainless steel,certain ceramics (e.g. alumina), certain polymers (e.g.tetrafluoropolyethylene, sold under the trade name “Teflon”), and othermaterials well known to one skilled in the art. Mount 100 is secured tomastoid 80 by any known attachment technique. Examples of attachmenttechniques include a self-tapping portion of mount 100, a lip portionextending radially from the proximal portion of mount 100 for receivinga bone screw or other fastener and securing mount 100 to mastoid 80, abiocompatible adhesive attachment, a receiving indentation in mastoid80, or another attachment technique known to one skilled in the art.

[0039] In FIG. 3, a piezoelectric transducer film 110 is carried bymount 100. Film 110 is secured to mount 100 at a first constraint point120 at the proximal end of mount 100 and is also secured to mount 100 ata second constraint point 130 at the distal end of mount 100. The directdistance between the first and second constraint points 120 and 130 isin a longitudinal direction 135 of mount 100. Film 110 is bowed awayfrom mount 100 between the first and second constraint points 120 and130. The distance between first and second constraint points 120 and 130along the bowed surface of film 110 defines a length of the film 110. Adriving point 140 of film 110, intermediate between the first and secondconstraint points 120 and 130, is mechanically coupled within middle ear35 to an auditory element, such as the head portion of stapes 50. In oneembodiment, driving point 140 is adhesively affixed to the head portionof stapes 50. Film 110 is secured to mount 100 at the first and secondconstraint points 120 and 130 by any suitable technique such as by amechanical fastener, by an adhesive, or by forming receptacles in mount100 at first and second constraint points 120 and 130 for receiving andconstraining film 110 such that the film 110 is under tension and heldin place by the receptacles.

[0040] In FIG. 3, film 110 is a highly piezoelectric film such as apolarized fluoropolymer, e.g. polyvinylidene fluoride (PVDF). For thisapplication, a PVDF film such as that sold under the trademark “Kynar”by AMP, Inc., of Harrisburg, Pennsylvania, is the preferred material forfilm 110. Film 110 receives an electrical input signal, representingtransduced sounds, from an electronics unit 150 implanted in a cavity ofmastoid 80 as part of a MEI hearing system. The electronics unit 150couples the electronic input signal across a thickness 160 of film 110through its output leads 170 and 180 to respective connection points 171and 181, located across thickness 160 of film 110 at any convenientpoints. Alternating polarities of the applied electrical input signalcause variations in the length of film 110. Film 110 is mechanicallycoupled to stapes 50 to define the location of a driving point 140,which is approximately midway between first and second constraint points120 and 130 or selectably located elsewhere on film 110. Film 110 isoptionally also affixed to stapes 50 at driving point 140.

[0041] By constraining the film 110 at first and second constraintpoints 120 and 130, driving point 140 is deflected toward and away frommount 100 when the length of film 110 decreases and increasesrespectively. Thus, variations in the length of film 110 are transformedinto positional variations of driving point 140 that are typicallyapproximately orthogonal to the longitudinal direction 135 of mount 100.Forces resulting from the positional variations of driving point 140 aremechanically coupled to the head portion of stapes 50, causingmechanical vibrations of stapes 50, which are transmitted to cochlea 60at oval window 55.

[0042]FIG. 4 illustrates an electromechanical input transducerembodiment of the invention. Film 110 is bowed away from mount 100toward malleus 40. Film 110 is mechanically coupled, and optionallyaffixed, to malleus 40 to define a vibrated point 190, which isapproximately intermediate on film 110 between first and secondconstraints 120 and 130, or selectably located elsewhere on film 110.Sounds received at tympanic membrane 30 cause vibrations in malleus 40,which in turn cause positional variations in vibrated point 190 that aretypically approximately orthogonal to the longitudinal direction 135 ofmount 100. Forces resulting from the positional variations in vibratedpoint 190 impart a stress in the length of film 110, which in turnproduces a resulting electrical output signal across thickness 160 offilm 110. The electrical output signal across thickness 160 of film 110is provided to electronics unit 150 at connection points 201 and 211,located across thickness 160 of film 110 at any convenient points, torespective input leads 200 and 210.

[0043]FIG. 5 illustrates an electromechanical output transducerembodiment of the invention in middle ear 35. Hoop-shaped piezoelectrictransducer film 220 is carried by mount 100. Film 220 is interposedbetween mount 100 and stapes 50. Film 220 comprises the same materialdescribed above with respect to film 110. Film 220 is mechanicallycoupled to mount 100 at a coupling point 230, and preferably secured bya mechanical fastener, biocompatible adhesive attachment, or equivalenttechnique. First and second arms 240 and 250 each extend outwardradially from mount 100. First and second arms 240 and 250 mechanicallyconstrain, and are optionally secured, to film 220 at respective firstand second constraint points 260 and 270. A circumferential distancealong the hoop-shaped inner surface of film 220 defines acircumferential length of film 220. Film 220 is mechanically coupled,and optionally affixed, to stapes 50 to define the location of drivingpoint 140, which is approximately intermediate on film 220 between firstand second constraints 260 and 270, or selectably located elsewherealong the circumference of film 220.

[0044] In FIG. 5, film 220 receives an electrical input signal,representing transduced sounds, from an electronics unit 150 implantedin a cavity of mastoid 80 as part of a MEI hearing system. Electronicsunit 150 applies the electrical input signal at electronics unit 150through its output leads 170 and 180 to connection points 171 and 181,respectively located across the thickness 160 of the film 220 at anyconvenient points. Alternating polarities of the applied electricalinput signal cause variations in the circumferential length of film 220.By constraining film 220 at first and second constraint points 260 and270, driving point 140 is deflected toward and away from mount 100 whenthe circumferential length of film 220 decreases and increasesrespectively. Thus, variations in the circumferential length of film 220are deflected into positional variations of driving point 140 that aretypically approximately orthogonal to the longitudinal direction 135 ofmount 100. Forces resulting from the positional variations of drivingpoint 140 are mechanically coupled to the head portion of stapes 50,causing mechanical vibrations of stapes 50, which are transmitted tocochlea 60 at oval window 55. If the circumferential length of thehoop-shaped film 220 of FIG. 5 exceeds the length of the bow-shaped film110 of FIG. 3, and film 110 is not secured at first and secondconstraint points 260 and 270, a larger positional variation in drivingpoint 140 will result in the embodiment of FIG. 5 for the samefractional change in length produced by the applied electrical signal.

[0045]FIG. 6 illustrates an electromechanical input transducerembodiment of the invention. Film 220 is interposed between mount 100and malleus 40. Film 220 is mechanically coupled, and optionallyaffixed, to malleus 40 to define the location of vibrated point 190,which is intermediate on film 220 between first and second constraintpoints 260 and 270, or selectably located elsewhere along thecircumference of film 220. Sounds received at tympanic membrane 30 causevibrations in malleus 40, which in turn cause positional variations at avibrated point 190. The positional variations at vibrated point 190 aretypically approximately orthogonal to the longitudinal direction 135 ofmount 100. Forces resulting from positional variations in vibrated point190 impart a stress in the circumferential length of film 220, which inturn produces a resulting electrical output signal across thickness 160of film 220. The electrical output signal across thickness 160 of film220 is provided to electronics unit 150 through input leads 200 and 210electrically coupled to connection points 201 and 211, respectivelylocated across the thickness 160 of the film 220 at any convenientpoints.

[0046]FIG. 7 illustrates an electromechanical output transducerembodiment of the invention in middle ear 35. Piezoelectric transducerfilm 280 is, in one embodiment, a bi-element transducer film carried bymount 100. A bi-element transducer film comprises two film elements thatare bonded together such that they amplify a piezoelectric action in adirection approximately normal to the bonding plane. Such a bi-elementtransducer vibrates according to a potential difference applied betweentwo bonded film elements.

[0047] Film 280 is interposed between mount 100 and stapes 50. Eachelement of film 280 comprises the same material described above withrespect to film 110. First and second arms 240 and 250 each extendoutward radially from mount 100. First and second arms 240 and 250 aremechanically coupled, and preferably secured, to film 280 at respectivefirst and second constraint points 290 and 300. Film 280 is mechanicallycoupled, and optionally affixed, to stapes 50 to define the location ofdriving point 140, which is intermediate on film 280 between first andsecond constraint points 290 and 300, or selectably located elsewhere onfilm 280.

[0048] In FIG. 7, film 280 receives an electrical input signal,representing transduced sounds, from an electronics unit 150 implantedin a cavity of mastoid 80 as part of a MEI hearing system. Electronicsunit 150 applies the electrical input signal through its output leads170 and 180 at connection points 171 and 181, respectively locatedacross the thickness 160 of the film 280 at any convenient points.Alternating polarities of the applied electrical input signal causedeflections in driving point 140 toward and away from mount 100 when thelength of film 280 decreases and increases respectively. The positionalvariations of driving point 140 are typically approximately orthogonalto the longitudinal direction 135 of mount 100. Forces resulting fromthe positional variations of driving point 140 are mechanically coupledto stapes 50, causing mechanical vibrations of stapes 50, which aretransmitted to cochlea 60 at oval window 55.

[0049]FIG. 8 illustrates an electromechanical input transducerembodiment of the invention. Film 280 is interposed between mount 100and malleus 40. Film 280 is, in one embodiment, a bi-element transducerfilm, as described above. Film 280 is mechanically coupled, andoptionally affixed, to malleus 40 to define the location of vibratedpoint 190, which is intermediate on film 280 between first and secondconstraint points 290 and 300, or selectably located elsewhere on film280. Sounds received at tympanic membrane 30 cause vibrations in malleus40, which in turn cause positional variations at a vibrated point 190.The positional variations at vibrated point 190 are typicallyapproximately orthogonal to the longitudinal direction 135 of mount 100.Forces resulting from positional variations in vibrated point 190produce a resulting electrical output signal across thickness 160 offilm 280. The electrical output signal across thickness 160 of film 280is provided to electronics unit 150 at its input leads 200 and 210,respectively, across the thickness 160 of the film 280 at any convenientpoints.

[0050]FIG. 9 illustrates an electromechanical output transducerembodiment of the invention in middle ear 35. Piezoelectric transducerfilm 300 is carried by mount 100. Film 300 comprises the same materialdescribed above with respect to film 110. Film 300 is secured to mount100 at first constraint point 290. Film 300 is mechanically coupled, andoptionally affixed, to stapes 50 to define the location of driving point140, which also serves as a second constraint point.

[0051] In FIG. 9, film 300 receives an electrical input signal,representing transduced sounds, from an electronics unit 150 implantedin a cavity of mastoid 80 as part of a MEI hearing system. Electronicsunit 150 applies the electrical input signal through its output leads170 and 180 at connection points 171 and 181, respectively locatedacross the thickness 160 of the film 300 at any convenient points.Alternating polarities of the applied electrical input signal causedeflections of driving point 140 toward and away from mount 100. Forcesresulting from the positional variations of driving point 140 aremechanically coupled to the head portion of stapes 50, causingmechanical vibrations of stapes 50, which are transmitted to cochlea 60at oval window 55.

[0052]FIG. 10 illustrates an electromechanical input transducerembodiment of the invention. Film 300 is secured to mount 100 at firstconstraint point 290. Film 300 is mechanically coupled, and optionallyaffixed, to malleus 40 to define the location of vibrated point 190.Sounds received at tympanic membrane 30 cause vibrations in malleus 40,which in turn cause positional variations at a vibrated point 190. Thepositional variations at vibrated point 190 in turn produces a resultingelectrical output signal across thickness 160 of film 300. Theelectrical output signal across thickness 160 of film 300 is provided toelectronics unit 150 through its input leads 200 and 210 at connectionpoints 201 and 211, respectively located across the thickness 160 of thefilm 300 at any convenient points.

[0053] As an input electromechanical transducer in the above describedembodiments, mechanical vibrations are typically received from malleus40. Such vibrations typically have displacements in the range between1-100 nanometers at audio frequencies and typically averageapproximately 5 nanometers for 80 dB sound pressure level (SPL) attympanic membrane 30. As an output electromechanical transducer in theabove described embodiments, the invention is capable of producingmechanical vibrations at stapes 50 that include the range of stapedialdisplacements typically found in a normal auditory system. A sound levelof 80 dB SPL at tympanic membrane 30 typically corresponds to adisplacement in a range between 0.2 to 2.5 nanometers.

[0054]FIG. 11 illustrates an embodiment of the hearing assistance systemthat also includes an external (i.e., not implanted) programmer 1100,which is communicatively coupled to an external or implantable portionof the hearing assistance device, such as electronics unit 150.Programmer 1100 includes handheld, desktop, or a combination ofhand-held and desktop embodiments, for use by a physician or the patientin which the hearing assistance device is implanted.

[0055] In one embodiment, each of programmer 1100 and the hearingassistance device include an inductive element, such as a coil, forinductively-coupled bi-directional transdermal communication betweenprogrammer 1100 and the hearing assistance device. Inductive coupling isjust one way to communicatively couple programmer 1100 and the hearingassistance device. Any other suitable technique of communicativelycoupling programmer 1100 and the hearing assistance device may also beused including, but not limited to, radio-frequency (RF) coupling,infrared (IR) coupling, ultrasonic coupling, and acoustic coupling.

[0056] In one embodiment, the signals are encoded using pulse-codemodulation (PCM), such as pulse-width telemetry or pulse-intervaltelemetry. In pulse-width telemetry, communication is by short bursts ofa carrier frequency at fixed intervals, wherein the width of the burstindicates the presence of a “1” or a “0”. In pulse-interval telemetry,communication is by short fixed-length bursts of a carrier frequency atvariable time intervals, wherein the length of the time intervalindicates the presence of a “1” or a “0”). The data can also be encodedby any other suitable technique, including but not limited to amplitudemodulation (AM), frequency modulation (FM), or other communicationtechnique.

[0057] The data stream is formatted to indicate that data is beingtransmitted, where the data should be stored in memory (in theprogrammer 1100 or the hearing assistance device), and also includes thetransmitted data itself. In one embodiment, for example, the dataincludes an wake-up identifier (e.g., 8 bits), followed by an address(e.g., 6 bits) indicating where the data should be stored in memory,followed by the data itself.

[0058] In one embodiment, such communication includes programming of thehearing assistance device by programmer 1100 for adjusting hearingassistance parameters in the hearing assistance device, and alsoprovides data transmission from the hearing assistance device toprogrammer 1100, such as for parameter verification or diagnosticpurposes. Programmable parameters include, but are not limited to:on/off, standby mode, type of noise filtering for a particular soundenvironment, frequency response, volume, gain range, maximum poweroutput, delivery of a test stimulus on command, and any other adjustableparameter. In one embodiment, certain ones of the programmableparameters (e.g., on/off, volume) are programmable by the patient, whileothers of the programmable parameters (e.g., gain range, filterfrequency responses, maximum power output, etc.) are programmable onlyby the physician.

[0059] Though the drawings illustrate the invention coupled to themalleus 40 when used as an input electromechanical transducer andcoupled to the stapes 50 when used as an output electromechanicaltransducer, the invention may also be coupled to other auditory elementswithin the middle ear 35. Also, incus 45 need not be removed. Forexample, the invention may also be coupled to receive mechanicalvibrations from the tympanic membrane 30 or the malleus 40. In anotherexample, the invention may also be coupled to vibrate incus 45, ovalwindow 55, round window 65, vestibule 61, or semicircular canals 62.

[0060] For clarity, the above described embodiments have been describedwith respect to function as either electromechanical input or outputtransducers. The piezoelectric effect allows bothmechanical-to-electrical and electrical-to-mechanical transducing.Accordingly, each of the above described embodiments are intended tofunction as either electromechanical input transducers for sensingmechanical vibrations, or as electromechanical output transducers forproducing mechanical vibrations. In particular, the above describedembodiments may be switched between vibrating and vibrated auditoryelements to obtain the desired functionality, and electrical signals canbe accordingly coupled to an electronics unit of either a P-MEI or T-MEIhearing aid, or other at least partially implantable hearing system suchas a cochlear implant with middle ear vibration sensing. Also, inventiveconcepts illustrated in particular embodiments are intended to alsoapply to the other embodiments disclosed herein.

[0061] By utilizing the piezoelectric films described above, theinvention provides several advantages over ceramic piezoelectrictransducers sometimes used in MEI hearing systems. PVDF films offer arelatively flat frequency response over a wide frequency range. PVDFfilms are particularly desirable as input electromechanical transducersfor sensing mechanical vibrations since they provide a higher voltageoutput in response to an applied force input than a piezoelectricceramic material. PVDF films also have a high elastic compliance, whichallows malleus 40 to vibrate more freely when coupled at vibrated point190 to a piezoelectric film transducer than when coupled to apiezoelectric ceramic transducer material.

[0062] Thus, the invention provides a method and apparatus fortransducing between mechanical and electrical signals within a middleear to improve hearing using a piezoelectric transducer film inconjunction with an electronics unit of an implantable hearing systemsuch as a partial middle ear implantable (P-MEI) or total middle earimplantable (T-MEI) hearing system.

What is claimed is:
 1. An at least partially implantable hearingassistance system, comprising: a vibrator including a mount, adapted tobe secured to a middle ear and a piezoelectric transducer film, carriedby the mount, proportioned to be mechanically coupled to the middle earand to vibrate the auditory element in response to an electrical inputsignal; an electronics unit, electrically coupled for providing theelectrical input signal to the vibrator; and a programmer, adapted forcommunicative coupling to the electronics unit.
 2. The system of claim1, in which the film is secured at a plurality of constraint points. 3.The system of claim 2, in which the film is secured to transformlongitudinal variations in a physical dimension of the film intovibrations of the auditory element.
 4. The system of claim 2, in whichthe film has a hoop shape.
 5. The system of claim 2, in which the filmhas a substantially straight length.
 6. The system of claim 2, in whichthe film has a bow shape.
 7. The system of claim 2, further comprisingfirst and second arms, each extending radially outward from the mountand mechanically coupled to the film.
 8. The system of claim 2, in whichthe film comprises polyvinylidene fluoride.
 9. The system of claim 2, inwhich the piezoelectric transducer film is mechanically coupled to themount at first and second constraint points, and having between thefirst and second constraint points at least one driving point on thefilm coupled to an auditory element at the driving point such that avariation in a film length between the first and second constraintpoints is transformed into an approximately orthogonal variation inposition of the driving point for vibrating the auditory element. 10.The system of claim 2, in which the film is a bi-element transducerfilm.
 11. An at least partially implantable hearing assistance system,comprising: an electromechanical sensor, including a mount adapted to besecured to a middle ear, and a piezoelectric transducer film carried bythe mount, in which the film is proportioned for mechanically couplingto an auditory element in the middle ear, and the film is adapted forreceiving vibrations from the auditory element and producing a resultingoutput voltage in response to the vibrations; an electronics unit,electrically coupled for providing the electrical input signal to thevibrator; and a programmer, adapted for communicative coupling to theelectronics unit.
 12. The system of claim 11, in which the resultingoutput voltage is produced across a thickness of the film and providedto an electronics unit.
 13. The system of claim 11, in which the film issecured at a plurality of constraint points.
 14. The system of claim 11,in which the film is secured to transform vibrations of the auditoryelement into longitudinal dimensional variations of the film.
 15. Thesystem of claim 11, in which the film has a hoop shape.
 16. The sensorof claim 11, in which the film has a substantially straight length. 17.The sensor of claim 11, in which the film has a bow shape.
 18. Thesensor of claim 11, further comprising first and second arms, eachextending radially outward from the mount and mechanically coupled tothe film.
 19. The sensor of claim 11, in which the film comprisespolyvinylidene fluoride.
 20. The sensor of claim 11, in which the filmis coupled at a vibrated point to an auditory element within the middleear, and mechanically coupled to the mount at first and secondconstraint points such that vibrations received from the auditoryelement at the vibrated point produce a variation in a longitudinaldirection of the film which in turn produces a resulting output voltage.21. The sensor of claim 20, in which the resulting output voltage isproduced across a thickness of the film and provided to an electronicsunit.
 22. The sensor of claim 11, in which the film is a bi-elementtransducer film.